GB2413415A

GB2413415A - Method for creating a histogram

Info

Publication number: GB2413415A
Application number: GB0513905A
Authority: GB
Inventors: Andreas Loew
Original assignee: Thomson Licensing SAS
Current assignee: Thomson Licensing SAS
Priority date: 2003-01-16
Filing date: 2003-12-24
Publication date: 2005-10-26
Also published as: WO2004063938A2; JP2006513472A; DE10301407A1; WO2004063938B1; GB0513905D0; US20060147111A1; WO2004063938A3; AU2003298247A1; AU2003298247A8

Abstract

The invention relates to a method for creating a histogram representing the distribution of supplied quantities which are associated with supplied values within a pre-determined value range, said value range being divided into pre-determined partial ranges which are defined by supporting values. For values which lie between a supporting value and an adjacent supporting value, division factors are calculated according to the position thereof. The quantities are divided according to the respective division factors between the respective supporting value and the adjacent supporting value, and are separately accumulated according to supporting values. The accumulated values are divided by the number of division factors which are respectively separately accumulated according to supporting values.

Description

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DESCRIPTION

Method for creating a histogram

Technical Field

The Invention relates to a method for formation of a histogram that represents the distribution of supplied variables, which are associated with supplied values that are within a predetermined value range.

Background to the Invention

When analysing signals, it is frequently necessary to record variables, which are associated with individual values (sample values) of the signals, statistically separated according to their values. In this case, the variables to be recorded are frequently discrepancies from target values. In practice, the values are frequently within a wide value range of, for example, 1024 for ten-blt coding of an analog signal. In order to create a histogram, facilities for addition of the variables (accumulators) would then be required per se for each of these 1024 possible values. This involves considerable complexity.

Description of the invention

The method according to the invention allows the formation of such histograms with less effort, in that the value rarig is subdivided into predetermined sub-rangcs, which Abe- bounder! by support va lees/ In that sharing factors are c:,i]ulated for values which are between one support value and an adjacent support value, as a function of their position, In that the variables are distributed between the respective support value and the adjacent support value as a function of the respective sharing factors, and are accumulated separately on the basis of the support values, and In that the accumulated values are divided by the total number of sharing factors which have in each case been accumulated separately on the basis of the support values.

The method according to the invention is particularly suitable for use with digital video signals, in which case the variables represent discrepancies from the ideal signal profile resulting, in particular, from non-linearities of transmission elements that operate on an analog basis, such as optoe]ectrical transducers.

However, it Is also possible to form different histograms using the method according to the Invention, in particular for applications In which the variables do not fluctuate to a major extent from one value to the next.

A development allows subdivision between two adjacent accumulators in an advantageous manner in that a sharing factor is in each case derived from the difference between the supplied value and the support value, in that a further sharing factor is in each case formed by formation of the complementary value of the one sharing factor, In that the variables are each multiplied by the one sharing factor and by the other sharing factor, and in that both products, which are each associated with one variable, are accumulated in accumulators for adjacent value ranges.

The method according to the Invention can be carried out In such a way that the sharing factors are derived linearly from the differences.

Noweve:, t 1S also possible to take account of different Crar='Ter_cS of the variables, In particular of the discrepancies, by deriving the subdivision factors from the differences, using a non-linear function.

Brlef Descrlptlon of the Drawing One exemplary embodiment of the invention will be explained in more detail in the following description, and is illustrated:.n the form of a block diagram in the drawing.

Descrlption of the Exemplary Embodiment The exemplary embodiment as well as parts of it are actually illustrated as b].ock diagrams. However, this does not mean that the arrangement according to the invention IS restricted to an implementation with the aid of ndlvidual circuits which correspond to the blocks. In face, the arrangement according to the invention can be implemented in a particularly advantageous manner by means of large-scale integrated clrcults. In this case, It IS possible to use digital signal processors which, when programmed appropriately, carry out the processing steps illustrated in the block diagrams.

Inputs 1, 2 are supplied with the values VA (= value) and DE (= deviation) which are required to form the histogram, with DE being dependent on VA, and VA being able to assume a value range which results from the number of bits V. On the assumption that VA may assume 16 values, the number of bits is V=4. In addition, the example IS based on the assumption that N+ l=5 support values, specifically 0, 4, 8, 12, 16, are chosen for this value range, thus resulting In the overall value range being subdivided into N=4 sub- -;anc3e., Lr ecu of winch the variables DE are accumulated.

Jo this case, the support value 16 assumes a specks] pOS t Lou s.nce the vague 16 Is never reached with a 4-bit number, although it is required later for accumulation of the shares of the values which are above the support values for 12.

A value range or the support value which is the lower llmlt of the value range In which the respective value VA is located 1S chosen ln a selector 3. An address As for the respective value range is obtained by formation of the integer Int(VA*N/2^V), and is passed to changeover swlLches 4, 5. This ordinal number can assume the range O to N-1.

That support value which is subtracted from the value VA in element 7 is calculated from As by multiplication of the ordinal number by 2^V and division by N. thus resulting in a difference value D. This difference value can be influenced, for example made non-linear, In a

look-up table 8.

In the range of the value VA from O to 15 and the support values at 0, 4, 8 and 12, quoted by way of example, the difference value may be 0, 1, 2 or 3. If non-linearisation IS intended to be possible by means of the look-up table, finer quantization of the output values D' from the look- up table 3 is required, for example from O to 15. The following values are then obtained for a linear table: D 0 1 2 3 D' 0 4 8 12, while a non- ' inear table can be formed, for example, as follows: v 1 2 3 D' O L 4 '' lime 1, ! ferenc e 1,', ,vR:i t Her efore need r of necessary I y be the same as D, is used as sharing factor for distribution of the variables DE supplied at terminal 2 among two adjacent accumulators. For this purpose, the sharing factor D' IS passed directly to a first multiplier 10, and to a second multiplier 11 via a circuit 9 for formation of the complement K- D' as a further sharing factor. In the numerical example that has been used K equals 16. The output variables Io and Is from the multlpllers 10, 11 ar added, In each case, In one upper and one lower of two adjacent accumulators. The sharing factors D' and K-D1 are supplied as counting variables Co and Cu to an upper and a lower of two adjacent further accumulators (counting accumulators).

The accumulators are arranged in two groups 12, 13. The group 12 comprises accumulators from AkkuO to AkkuN, to which the variables Iu and To are passed via a changeover swlLch 4. The group 13 comprises counting accumulators (CAkkuO to CAkFuN), which are likewise driven via a changeover switch 5. The changeover switches 4, 5 are controlled by As.

If, by way of example, VA equals 7, the selector 3 emits As=1. The lower contacts of the changeover switches 4, 5 are thus moved to the position 1, and the upper contacts are moved to the position 2. When VA=7, then DA=3, which results In D'=12 for a linear look-up table 8. DE is thus multiplied by 12 in the multiplier 10, and by 16-12=4 in the multiplier 11. The Akku2 is accordingly supplied with twelve times DE, and Akkul with four times DE. The corresponding counting accumulators contain the values 12 and 4.

When a sufficiently large number of variables DE have been accumulated for a sufficiently large number of values VA, tile conlen:s of the accumulat:.'rs -l.2 are divided by the cor-terts of the o.nting accumulators 13, .r. computer 44. l'he resalt.s of this di.vsiorl then fcrrm a value of the histogram for each of the support values.

Claims

Patent Claims 1. A method for formation of a histogram using accumulators

which are associated with respective support points, wherein the range of the possible input values is subdivided into sub-ranges, which are bounded by two support values, wherein each support value has an associated accumulator, characterized in that a subtracter calculates the difference between the input value and a support value of the sub-range in which the input value is located, in that a first sharing factor is calculated from the difference, in that the complement value of che first sharing factor forms a second sharing factor, in that a multiplier multiplies the input value by the first and the second sharing factors, in that the products of the input values and of the sharing factors are accumulated by the accumulators which are associated with the support values, and in that a divider divides the accumulated values by the total number of sharing factors which have in each case been accumulated separately on the basis of the support values.
2. The method as claimed in claim 1, characterized in that the sharing factors are derived linearly from the differences.
3. The method as claimed in one of claims 1 or 2, characterized in that the sharing factors are derived from the differences by means of a nonlinear function.
4. Tree melrod as claimed an claim 3, characterized in that the ncri-linear fur-ction is stored in a look-up- laLe.
5. A circuit for formation of a histogram with accumulators, which are associated with respective support points, wherein the range of the possible input values is subdivided into sub-ranges, which are bounded by two support values, wherein each support value has an associated accumulator, characterized in that an input value is supplied via an input (VA) to a selector (3) by means of which a sub-range can be selected, which matches the input value, wherein an address signal. (As) is applied to selection switches for selection of the associated accumulator, in that a subtracter (7) is provided by means of which the value of the lower support value in the sub-range can be subtracted from the input value, in that the difference (D) is supplied as an input signal to a look-up-table (8), whose output signal (D') is a first sharing factor, in that the first sharing factor its supplied to a first multiplier (10), to which a discrepancy value (DA) is supplied as a further factor, and whose output. signal (To) is supplied to a first accumulator (12), which is selected by the address signal (As), in that the output value (D') from the look-uptable (8) is supplied as a first counting variable (Co) to a first counting accumulator (13) which is selected by means of the address signal (As), in that a complement circuit (9) forms the complement of the output signal (D') from the look-up-table (8), wherein the complement is supplied as a second counting variable (Cu) to a second counting accumulator (13) which is selected by means of the address signal, in that the complement is supplied to a second multiplier (11), to which the discrepancy value (DE) is supplied as a further factor, and whose output signal (Iu) is supplied to a second accumulator (12), which is selected by the address signal (As), and in that a divider circuit (14) divides the contents of the first and second accumulators (-12) by The conler,t-s of: the respectively associated counting accumulators (-13).